1. Technical Field
The present disclosure relates to an on-board radar apparatus and a region detection method.
2. Description of the Related Art
In recent years, a collision prevention system for preventing collision with an object (e.g., a vehicle or a pedestrian) by detecting an object around a vehicle on the basis of a received signal reflected by the object with the use of a radar (e.g., a millimeter-wave radar) has been developed.
Japanese Patent No. 5206579 discloses a method in which a radar apparatus mounted in a vehicle detects reflection points around the vehicle and groups predetermined ranges (segments) including the reflection points as a single object. The radar apparatus tracks the grouped segments over a plurality of frames.
However, in a case where targets to be detected by the conventional radar apparatus include a pedestrian or a roadside object, which is a weakly reflecting object, in addition to a vehicle, which is a strongly reflecting object, it is difficult for the conventional radar apparatus to distinguish an unnecessary wave (e.g., ground clutter) and a reflecting object. In the conventional radar apparatus, a power threshold value level used for detection of reflection points need be set high in order to remove an unnecessary wave. However, a signal reflected by a weakly reflecting object is, for example, susceptible to the influence of phasing, and therefore the power level of the reflected signal received by a radar apparatus is unstable.
Since the power threshold value level is set high in the conventional radar apparatus, it becomes more likely that the reception power of a signal reflected by a weak reflecting object which is a target to be detected is equal to or lower than the threshold value. Accordingly, the accuracy of detection of reflection points deteriorates.
In a case where a method of grouping reflection points for each object is used in the radar apparatus disclosed in Japanese Patent No. 5206579 that does not consider a signal reflected by a weakly reflecting object, processing for detecting objects including a weakly reflecting object is unstable. This problem need be dealt with.
Furthermore, targets to be detected by the radar apparatus disclosed in Japanese Patent No. 5206579 are objects whose sizes can be defined to some extent such as a vehicle. Therefore, in a case where grouping processing and tracking processing are performed on a roadside object, whose size or distinction is hard to define, by using size information in the radar apparatus disclosed in Japanese Patent No. 5206579, identification of an identical object between frames is unstable. This problem need be dealt with.